Definition of an Information Retrieval System (IRS) 

According to Sparck Jones an Information Retrieval System is a set of rules and procedures, for performing some or all of the following operations: 

1. Indexing (or constructing of representations of document). 
2. Search formulation (or constructing of representations of information needs). 
3. Searching (or matching representations of documents against representations of needs). 
4. Index language construction (or generation of rules of representation). 

In the foregoing definition, the basic functions of a computer-based storage and retrieval system are implied in general terms. But, in practice a large number of variants are often encountered in adapting a system to the user's requirements and methods used. 

Let us also examine another definition. According to Kowalski "An information retrieval system is a system that is capable of storage, retrieval and maintenance of information. Information in this context can be composed of text (including numeric and date data), images, audio, video and other multi-media objects. Although the form of an object in an IRS is diverse, the text aspect has been the only data type that lent itself to full functional processing. Other data types have been treated as highly informative sources but are primarily linked for retrieval based upon search of the text". [Kowalski, 1997]. Kowalski also states that an IRS consists of a software program that facilitates a user in finding the information he needs. The system may use standard computer hardware to support the search function. According to him, the success of an IRS depends on how well it can minimise the expenditure for a user to find ' the needed information.